Continuous blood cell separation and collection is a well-known process for collecting desired blood components, such as red cells, platelets or plasma from a donor. Typically whole blood is withdrawn from a donor and directed into a centrifugal processing chamber to separate the whole blood into its various therapeutic components. This is often carried out utilizing blood processing systems and methods comprising a durable centrifuge in association with a single-use, sterile fluid circuit that may include a processing chamber and associated storage containers, fluid flow tubing and the like. The processing chamber is usually mounted on a centrifuge rotor or bowl, which spins the chamber creating a centrifugal field, which separates the whole blood into its components based on their density.
Well-known and exemplary centrifugal blood processing systems include the Amicus® and Alyx® separators, available from Fenwal Inc. of Lake Zurich, Ill. The functional aspects of the Amicus® separator are disclosed in, e.g., U.S. Pat. Nos. 6,312,607 and 6,582,349, the entire disclosures of which are incorporated herein by reference.
In a centrifugal processing system such as the Amicus® separator, whole blood is typically separated into components in a two-stage process, using a belt-shaped processing container that has two separate processing chambers. The processing container is secured to a support in the form of a rotatable spool that is received within an outer bowl, such that the processing container is enclosed in an annular space between the spool and the bowl. The spool and bowl are rotated in unison about a common axis to centrifugally separate the whole blood into components. In the usual two-stage process for collecting platelets, whole blood is continuously separated into concentrated red blood cells (RBC) and platelet rich plasma (PRP) in the first separation chamber. The PRP is then directed to the second centrifuge chamber for separation into platelet concentrate (PC) and platelet reduced (or poor) plasma (PPP). The red cells and PPP are returned to the donor or stored in collection containers, and the platelet concentrate accumulates in the second chamber.
Under certain circumstances, it may be desirable to increase the concentration of the platelets in the platelet concentrate beyond that resulting from the second stage of the above-described process. This may be done by membrane filtration. Alternatively, further concentration of the platelets may be achieved by a process known as centrifugal elutriation.
Centrifugal elutriation is a method of separating cells suspended in a liquid medium by which a separation chamber is provided into which a liquid comprising cells suspended in a liquid medium is subjected to counteracting centrifugal and flow forces to create a fluidized bed of the cells within the separation chamber. After the fluidized bed is created, the smaller cells within the fluidized bed may then be drawn out of the separation chamber by introducing additional suspension into the chamber. As additional cells from the added suspension are introduced into the fluidized bed, an amount of the smaller cells is expelled from the fluidized bed into a separate collection receptacle.
By way of the present disclosure, an improved method and apparatus for concentrating platelets from platelet-rich plasma using centrifugal elutriation is provided.